The present invention relates to an image processing apparatus, an image processing method and the like to display image data on a display device that has resolution lower than that of the image data.
At present, in the case where a person photographs an image or obtains an image through broadcast and internet, the display resolution of that image data is typically different from the resolution of a display device actually displaying that image data. Particularly, there are many cases in which image data of high resolution are displayed on a display device of low resolution, such as a case in which image data photographed with a digital camera having an imaging device of several million pixels are displayed on an LCD (Liquid Crystal Display) of a mobile phone unit having limited display size and a limited number of pixels.
In the past, scaling has been performed by averaging a plurality of pixels and by linear interpolation, in the case where image data of high resolution is thus displayed on a display device of low resolution (for example, refer to Patent Reference 1).
This method of related art is explained with respect to a case in which what is called VGA image data 11 of horizontal 640 pixels×vertical 480 pixels (the number of total pixels are 307,200 pixels) are displayed on a QVGA display device 12 of horizontal 320 pixels×vertical 240 pixels (the number of total pixels are 76,800 pixels) as illustrated in FIG. 1.
In this case, it is typically practiced as a method of related art that values of total four pixels of horizontal two pixels and vertical two pixels in the VGA image data 11 are averaged and displayed on the QVGA display device 12.
Specifically, as shown on the left side of FIG. 2, values of four pixels (pixels 31, 32, 33 and 34) in the VGA image data 11 located at positions of horizontal 2n, 2n+1 and vertical 2m, 2m+1 are averaged when the horizontal 640 pixels of the VGA are put as 0, 1, - - - 2n, 2n+1, - - - 638, 639 (n is an integer of 0 through 319) and the vertical 480 pixels are put as 0, 1, - - - 2m, 2m+1, - - - 478, 479 (m is an integer of 0 through 239).
Then, the average value of those pixels 31 through 34 is displayed as shown in FIG. 3 on a pixel 35 located at a position of horizontal n and vertical m in the QVGA display device 12 as shown on the right side of FIG. 2. The value of the data thus displayed on the pixel 35 is constant without being chronologically changed when the VGA image data 11 constitute a still image.
The following table 1 shows a specific example of the value displayed on this pixel 35. When the values of the pixels 31 through 34 are RGB values of eight bits (0 through 255) as shown in the second through fifth rows of this table, the RGB values of the pixel 35 become values shown in the bottom row of this table.
TABLE 1RGBValue of Pixel 31000Value of Pixel 32632550Value of Pixel 331270255Value of Pixel 34191255255Averaged RGB Value95127127of Pixel 35
Although one pixel 35 in the QVGA display device 12 is described hereinbefore, similar processing is performed regarding all the values of n=0 through 319 and m=0 through 239, so that the VGA image data 11 can be converted and displayed on the QVGA display device 12.    [Patent Reference 1] Japanese Published Patent Application No. H10-21387 (paragraph numbers 0034 through 0038, FIGS. 1 through 3)